Disk drives are widely used in computers, consumer electronics and data processing systems for storing information in digital form. The disk drive typically includes one or more storage disks and one or more head suspension assemblies. Each head suspension assembly includes a slider assembly having an air bearing surface, and a read/write head that transfers information to and from the storage disk. The rotation of the storage disk causes the slider assembly to ride on an air bearing so that the read/write head is at a distance from the storage disk that is referred to as a “head-to-disk spacing” (also sometimes referred to herein as a “HtD spacing” or a “flying height”).
Because today's disk drives utilize storage disks having increasingly high densities of data tracks, decreasing the HtD spacing has become of great importance. However, this desire for a very small HtD spacing must be balanced with tribological concerns in order to avoid damage to the read/write head and/or the storage disk, as well as loss of data.
Further, a large variation in the HtD spacing from slider assembly to slider assembly can cause significant issues in the manufacturing and reliability of the disk drives. Additionally, maintaining a relatively small and consistent HtD spacing is further complicated by other factors such as thermal pole tip protrusion caused by thermal expansion of the read/write head during various disk drive operations. For example, during a write operation, the electrical resistance of the write element generates heat in and around the read/write head, resulting in thermal expansion of the write pole tips toward the storage disk. The situation is commonly referred to a write pole tip protrusion (“WPTP”). If the WPTP is too extensive, the slider assembly can unintentionally contact the storage disk, causing off-track writing, damage to the slider assembly, damage to the storage disk and/or a permanent loss of data.